Besieged Mafia boss Joseph Massino was hammered with three more murder charges yesterday, including the only known hit tied to the Bonanno family during his reign – a crime that could whack him with the death penalty.

Newly unsealed court papers describe in chilling detail how wiseguy Gerlando Sciascia, 65, was marked for death in March 1999 after criticizing a cokehead capo who was close to Massino.

The two reputed hit men who pumped six bullets into Sciascia’s head, neck and torso – Bonanno soldiers John Joseph Spirito and Patrick Defilippo – were rounded up by the feds yesterday.

The Bonanno boss, who now faces a total of five murder charges, has been behind bars since January.

He was also charged yesterday in the grisly murder of a former bodyguard to the late Mafia don Carmine Galante. Cesare Bonaventre was chopped into three pieces and tossed into vats of glue at a New Jersey factory in April 1984.

A third murder charge against Massino relates to a 1987 hit on Gabriel Infanti.